Attenuated embedded phase shift photomask blanks

ABSTRACT

An attenuating embedded phase shift photomask blank that produces a phase shift of the transmitted light is formed with an optically translucent film made of metal, silicon, nitrogen or metal, silicon, nitrogen and oxygen. A wide range of optical transmission (0.001% up to 20% at 193 nm) is obtained by this process. A post deposition process is implemented to obtain the desired properties (stability of optical properties with respect to laser irradiation and acid treatment) for use in industry. A special fabrication process for the sputter target is implemented to lower the defects of the film.

FIELD OF THE INVENTION

The present invention is directed to attenuated embedded phase shiftphotomask blanks and in particular to attenuated phase shift mask (APSM)materials and processes.

BACKGROUND OF INVENTION

Phase shift masks are gaining attention as the next generationlithographic technique for microelectronic fabrication due to theircapability to produce higher resolution images compared to theconventional binary photomasks. Among the several phase shiftingschemes, the attenuating embedded phase shifter proposed by Burn J. Lin,Solid State Technology, January issue, page 43 (1992), the teaching ofwhich is incorporated herein by reference, is gaining wider acceptancebecause of its ease of fabrication and the associated cost savings.There have been a number of variations associated with this scheme toimprove the optical properties of the photomask, i.e. tunability of theoptical transmission and resistance against photon irradiation andchemical treatments.

The attenuated phase shift mask (APSM) described in U.S. Pat. No.5,897,977 to Carcia et al. consists of alternating layers of opticallytransmissive materials and optically absorbing materials. The advantageclaimed by this process is that the phase shift and transmission can becontrolled easily by adjusting the thickness of either or both of thelayers. However, the deposition process is complicated since twodifferent materials need to be deposited in an alternating sequence,which will increase the cost of the process and increase potentialdefects in the mask. Also, due to the different etching properties ofthe two materials, obtaining a smooth line edge by etching is difficult.

The APSM described in U.S. Pat. No. 5,939,227 to Smith consists of amultilayer of Si_(x)N_(y) and metal nitride. The advantage claimed bythis process is both materials are chemically stable and etchselectivity is well defined. However, the deposition of this process iscomplicated since it requires two separate targets and a planetarysample stage, which increases the cost for manufacturing and againsignificantly increases potential defect levels.

A Zr-based APSM described in U.S. Pat. No. 5,935,735 to Okubo et al.,wherein the film had 2 to 15% transmittance and less than 30%reflectivity. The Zr-based film consisted of two or more multilayerswith different optical properties to achieve the above transmittance andreflectivity. While this scheme provides good tunability, a multilayerstructure may not provide good manufacturability. Also, due to thehighly stable nature of Zr compounds, the RIE etch selectivity isinferior.

The APSM described in U.S. Pat. Nos. 5,942,356 and 6,153,341 to Mitsuiet al., consists of molybdenum, silicon and nitride. The advantageclaimed of this process is that it consists of a single material whichgives good etch properties. Also, the material is stable during laserirradiation and acid treatment. However, the tunability of % T is not asflexible as the multilayer materials. Mitsui et al., does notincorporate a post-deposition treatment in their patent.

Herein we describe a method to fabricate, through deposition and postdeposition treatment, a phase shift photomask that has tunable opticaltransmission, coupled with stable optical properties during usage(photon exposure and chemical treatments) of the photomask.

The present invention provides a phase shift photomask with a smallsurface roughness and low defect density by reducing the particulatesproduced during the deposition process.

We have also discovered that when the phase shift mask or phase shiftmask blank is annealed to a temperature higher than room temperatureunder an atmosphere which contains oxygen at more than 10⁻³ torr partialpressure, a film structure can be produced that is stable against photonirradiation and chemical treatments for photomask fabrication.

SUMMARY OF THE INVENTION

A broad aspect of the present invention comprises an attenuatingembedded phase shift photomask blank capable of producing a phase shiftof 180° with an optical transmission of at least 0.001% at a selectedlithographic wavelength, having chemical and optical durability andflexible optical transmission tunability.

In another aspect, the invention comprises a process of making anattenuating embedded phase shift photomask, which process comprises thesteps of depositing a thin film phase shifting material.

In another aspect, the invention comprises a process of making anattenuating embedded phase shift photomask, which uses a compositetarget with high material density and high discharge stability duringthe deposition process.

In another aspect, the invention comprises a process for stabilizationand improvement of the optical characteristics of the phase shiftingmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will become apparent upon a consideration of the followingdetailed description and the invention when read in conjunction with thedrawing Figures, in which:

FIG. 1 is a bar graph showing the Root mean square (RMS) roughness ofthe deposition using three different targets. The RMS roughness ismeasured over a 2000 Å×2000 Å scan area of an Atomic Force Microscope(DI5000, tapping mode). The RMS roughness is 0.80, 0.39 and 0.20 nm forfilms deposited with Dual target, Hot pressed target, and HIP target,correspondingly.

FIG. 2 is a summary of the RBS analysis of various films deposited undersingle target configuration.

FIG. 3A is a graph showing the relationship between the transmission (%T) at 193 nm wavelength and the N₂ flow (sccm) for the compositecathode(Si_(0.7)(TiSi₂)_(0.1)). All were deposited at 15 sccm Ar flow.

FIG. 3B is a graph showing the relationship between refractive index (n)at 193 nm wavelength and the N₂ flow (sccm) for the same samples in FIG.3A.

FIG. 3C is a graph showing the relationship between extinctioncoefficient (k) at 193 nm wavelength and the N₂ flow (sccm) for the samesamples in FIG. 3A.

FIG. 4 is a plot of the Transmission and Reflectivity as a function ofwavelength from 190 to 900 nm.

FIG. 5 XPS analysis of the deposited thin films. (a) surface and bulkcompositions of the thin films before and after annealing. (b) A depthprofile plot of embodiment 9. The sputter time is proportional to thefilm thickness, zero minute indicates the surface.

FIG. 6 is a graph showing the relationship between the transmission (%T) at 193 nm wavelength and the laser dosage (kJ/cm²). Two samples,annealed and unannealed, are plotted together for comparison. Theannealed sample shows an improved stability compared to the unannealedsample. The laser power density was 1.75 mJ/cm²/pulse at 100 Hzfrequency.

FIG. 7 is a summary of the % T changes after executing three differentpost-deposition processes (air anneal, N₂ anneal, and oxygen plasmatreatment) and % T changes after laser irradiation.

FIG. 8 is a graph showing the relationship between the transmission (%T) at 193 nm wavelength and the duration time of film exposed to amixture of H₂SO₄:H₂O₂=10:1 at 95° C. (also known as piranha solution).The % T change was 0.19% over 60 min immersion in the solution.

FIG. 9 is a summary of the RBS analysis and optical properties of filmsdeposited with various oxygen partial pressures.

FIG. 10 is a summary of the RBS analysis for various samples depositedunder dual target configuration.

FIG. 11A is a graph showing the relationship between the transmission (%T) at 193 nm wavelength and the power (watt) applied to the Ti cathodefor the deposition of Si_(w)Ti_(x)N_(y) and Si_(w)Ti_(x)N_(y)O_(x) usingco-sputtering from two pure targets: silicon nitride (Si₃N₄) andtitanium (Ti).

FIG. 11B is a graph showing the relationship between the refractiveindex (n) at 193 nm wavelength and the power (watt) applied to the Ticathode for the same samples in FIG. 11A.

FIG. 11C is a graph showing the relationship between the extinctioncoefficient (k) at 193 nm wavelength and the power (watt) applied to theTi cathode for the same samples in FIG. 11A.

DETAILED DESCRIPTION

A process is discovered for fabricating photomask blanks that producesphase shifting films having tunable optical characteristics (% T, n andk) (T is the transmission; n is the index of refraction; and k is theextinction coefficient) with 180° phase shift at 193 nm and withsignificantly enhanced exceptional stability against laser irradiationand chemical treatment. The phase shifting films comprise of silicon anda metal and nitrogen and/or oxygen. The metal can be an element from thegroups II, IV, V, transition metals, lanthanides and actinides. Anexample will be given for titanium as the metal. The invention comprisesa thin phase shifting film (Si_(w)Ti_(x)N_(y) or Si_(w)Ti_(x)N_(y)O_(z),where w is in the range 0.1 to 0.6, x is in the range 0.01 to 0.2, y isin the range 0 to 0.6, z is in the range 0 to 0.7.) deposited on asubstrate (quartz, Al₂O₃, etc) with a thin oxygen rich layer on thesurface and the methods for forming the films and enhancing theircharacteristics.

1. Deposition

The initial thin film can be deposited by sputter deposition (RF, DCmagnetron, AC magnetron, pulsed bipolar DC magnetron, RF diodesputtering, or other sputter deposition methods familiar to thoseskilled in the art) from either a single target of a composite material(Si_(1−x)Ti_(x), with x in the range 0.01 to 0.5) or two or more targetsof different compositions (for example, Si₃N₄ and Ti targets, orSi_(1−x)Ti_(x) and Ti targets). Variation in composition of thecomposite targets or individual variation of power and deposition timeof the pure targets produces changes in film composition. Reactivesputtering with nitrogen and oxygen provides further capability toadjust the relative compositions of Si, Ti, and N and O, and thus theoptical characteristics of the film. The substrate stage can be eitherstationary or planetary for the single target, and planetary for themultitarget with rotation speed adjusted accordingly.

Specifically, a RF magnetron sputtering was used for a single target(Si_(0.7)(TiSi₂)_(0.1)) deposition and a RF and DC magnetronco-deposition was used for dual target (Si₃N₄ and Ti) deposition.

2. Post-Deposition Modification of Film Structure

The surface layer of the deposited film becomes oxygen rich when exposedto air but is still unstable against radiation and chemical treatment.Subsequent heat treatment (air annealing) produces a much enhancedstability. X-Ray Photoelectron Spectroscopy (XPS) results show about 2%increase in the oxygen concentration of the surface after annealing at225° C. in air atmosphere. This surface enhancement can be accomplishedby either air annealing at elevated temperature or other gas mixtures orplasma treatment in an oxidizing environment.

The enhanced stability can be attributed to the fact that the change ofoptical properties during irradiation is due to the photon inducedoxidation under oxidizing atmosphere. Thus, by pre-oxidizing the surfacewith the described methods, the optical properties of the deposited filmshow an enhanced stability against irradiation. Details of thepost-deposition modification is described in section 5 (A).

3. Optical Properties

The optical properties (index of refraction (n), and extinctioncoefficient (k)) were determined using an n&k spectrophotometer in therange of 190 to 900 nm. The transmission at 180° phase shift wascalculated by using these n and k values.

4. Fabrication Process of the Si_(0.7)(TiSi₂)_(0.1) Target

A special target for the composite cathode is utilized. Instead ofmixing Ti and Si elements, a mixture of TiSi₂ and Si was used. It wasreported, U.S. Pat. No. 5,686,206, paragraph 6, line 56-67, that thedischarge during sputter deposition becomes unstable as the silicon tometal ratio increases. In particular, for Mo and Si, the dischargebecame unstable for targets with Si larger than 95 mol percent. Theproblem is due to low conductivity at the target surface since SiN_(x),which is an insulator, is formed during the process.

By utilizing the described process, we were able to increase the metalto silicon ratio increased from 1/9 to 1/7 (i.e., 28% increase of themetal to silicon ratio), thereby decreasing the amount of SiN_(x) layer.The target consists of 10 atomic percent of Ti in the form ofSi_(0.7)(TiSi₂)_(0.1) instead of Ti_(0.1)Si_(0.9).

Also, to reduce the particulate formation during the deposition, thetarget can be made using a HIP (hot isostatic pressing) process. The HIPprocess typically yields an increase in the density of the target ascompared to the conventional hot pressing process. The improveddensification varies with material properties but generally leads to, areduction of particulate levels in the sputter deposited films whichreduces the defects and surface roughness, as well as improving thetarget machinablility and strength. Hot pressed targets of this materialexhibited a density of 2.085 which is 75% of the theoretical density of2.78. HIP targets of this material possess densities of 96-98% oftheoretical values without interconnecting voids, resulting insignificant improvements to the strength and particulate levels of thetarget.

To demonstrate the improvement of the surface roughness, the AtomicForce Mircroscope data is shown in FIG. 1. The RMS roughness was takenover 2000 Å×2000 Å area for three different deposition conditions. Thefirst was the dual target deposition (Hot pressed target(Si_(0.7)(TiSi₂)_(0.1)) in RF with Hot pressed Ti target in DC), thesecond was the conventional Hot pressed target (Si_(0.7)(TiSi₂)_(0.1)),the third was a HIP processed target (Si_(0.7)(TiSi₂)_(0.1)). Thethickness of the film was 670 Å for all three samples. The dual targetdeposition was the roughest (0.8 nm), then the Hot pressed target (0.39nm), and the HIP processed target gave smoothest surface RMS roughness(0.20 nm) with 15% uncertainty of the measurement.

5. EXAMPLES

(A). Si_(w)Ti_(x)N_(y) or Si_(w)Ti_(x)N_(y)O_(z) Photomask BlanksPrepared by Single Target

1) Processing Gas Ar/N₂

Thin films composed of Si_(w)Ti_(x)N_(y) or Si_(w)Ti_(x)N_(y)O_(z) byusing a Si_(0.7)(TiSi₂)_(0.1) target were deposited, with the substratein a rotating holder with planetary motion or positioned under thetarget without planetary motion. Sputtering was carried out in anargon/nitrogen mixture with 1.0˜5.0 mT Ar partial pressure. Ultra highpurity gases were used for both Ar and N₂ (99.999%) and the backgroundpressure of the chamber was <9.0×10⁻⁷ torr. The thin film was depositedby RF magnetron sputtering from a five inch diameter target with a powerof 450 W. Under the above conditions, the deposition rate was typically0.6 to 1.6 Å/sec.

Prior to sputtering, the target was presputtered in 5 mT Ar for 5 min at450 W. Then 5 min of presputtering was performed under the depositioncondition of the thin film to precondition the surface of the target.After presputtering, the substrates were immediately loaded through aload lock chamber into the deposition chamber and deposition was carriedout. The film thickness ranged between 400 to 2000 Å depending on thedeposition conditions. FIG. 2 summarizes the film deposition conditionsand the resulting composition obtained from RBS analysis.

FIG. 3A. summarizes the % T calculated for films at 180° phase shiftversus the N₂ flow. The % T increases with increasing N₂ flow from 6-9sccm, beyond which little change is observed with higher N₂ flow. TheRBS result shows that the amount of N₂ incorporated into the filmincreases with N₂ flow until about 9 sccm, then changes little withfurther increase of N₂ flow. FIGS. 3B and 3C summarize the n and kvalues as a function of N₂ flow and deposition pressure, respectively.The RBS analysis shows an increasing oxygen concentration in the film asthe deposition pressure increases. The optical properties, n and k aredependent on the N and O concentration of the film and the density ofthe film. Higher deposition pressure reduces the film density andreduces the n value.

The reason for increasing O incorporation as the deposition pressureincreases is thought to be the following. The increasing pressurereduces the kinetic energy of the ions and radicals in the plasma(shorter mean free path), and thus makes background oxygen easier tostick to the surface as materials are being deposited.

FIG. 4 is an example of the transmission and reflectivity curvesmeasured from the n&k analyzer. The sample was deposited at 1 mT, Arflow 15 sccm, N₂ flow 9 sccm, thickness 679 Å, followed by an air annealat 225° C. for 15 min. For this thickness, the phase shift calculatedfrom the n and k value at 193 nm is 183.1 degrees. The transmission at193 nm was measured as 5.72%. The film composition measured by RBS is Si39 atomic %, Ti 3.3 atomic %, N 57 atomic %, O<1 atomic %.

FIG. 5(a) is an XPS analysis of the surface and bulk concentration oftwo embodiments before and after post-deposition process. Depositioncondition for embodiment 9 is 1 mT, N₂ flow—9 sccm, and RF power—450 W,film thickness 679 Å. Deposition condition for embodiment 10 was 5 mT,N₂ flow—9 sccm, and RF power—450 W, film thickness 890 Å. In thisexample, the process involves 225° C. annealing in air atmosphere for 15minutes. The oxygen concentration of the surface increases about 2%after the annealing for both embodiments. While the oxygen concentrationincrease of the bulk film was not detected, it is possible a smallamount (below the XPS detection limit, <1%) bulk oxygen increase couldhave occurred and affect the optical property. FIG. 5(b) is a depthprofile of the chemical concentration of embodiment 9. The sputter timeincrease corresponds to the film thickness increase.

FIG. 6 summarizes the change of % T at 193 nm as a function of Ar-Flaser at 193 nm (Lambda Physik LPX 120) irradiation with and without thepost-deposition process. The samples were prepared at depositionpressure 1 mT of Ar with N₂ at 9 sccm, RF power of 450 W. The filmthickness corresponded to 679 Å. In order to perform irradiationstudies, two films under the identical conditions were deposited on thesubstrate. The second film was annealed in air atmosphere at 225° C. for15 minutes. These films were both irradiated with laser power density of1.75 mJ/cm²/pulse at 100 Hz frequency. The unannealed film showssignificant radiation instability (>0.5% increase in transmission)especially during the first kJ of irradiation. The huge Transmissionincrease after the first kJ is no longer present in the annealed sample.The total transmission change at a dose of 5.4 kJ/cm² is 0.27%. Notethat there is transmission change caused by annealing (0.42%).

Other examples of post-deposition process include oxygen plasmatreatment and annealing under nitrogen atmosphere. The comparison of thetwo with air anneal is shown in FIG. 7. The increase of the % T afteroxygen plasma treatment is comparable to the air annealing at 225° C.for 15 minute. The % T increase is smaller for the N₂ annealing at 225°C. for 15 min. compared to the other two processes. Also, the N₂annealing improves the stability of the film to some degree due to thefinite amount of oxygen background pressure. However, the stability isinferior to the air annealed result. For example, in FIG. 7, the % T ofthe air annealed sample increased 0.27% over laser dosage of 5.4 kJ/cm²,while the % T of the N₂ annealed sample increased 0.32% over dosage of2.2 kJ/cm², already exceeding the % T for the air annealed sample atless than half of the laser dose.

FIG. 8 summarizes the change of % T at 193 nm as a function of immersiontime in a cleaning solution of sulfuric acid and hydrogenperoxide(H₂SO₄:H₂O₂=10:1, 95° C.), this solution is typically used forstripping photoresists in manufacturing line, also known as piranhasolution. The deposition and post-deposition process is identical to thefilm described in FIG. 6. The total change of % T is 0.19% over 60 minof immersion. This excellent stability ensures a compatibility of thematerial with the standard photomask manufacturing process.

2) Processing Gas Ar/N₂/O₂

Thin films composed of Si_(w)Ti_(x)N_(y)O_(z) by using aSi_(0.7)(TiSi₂)_(0.1) target were deposited, with the substrate in arotating holder with planetary motion or positioned under the targetwithout planetary motion. Sputtering was carried out in anargon/nitrogen/oxygen mixture processing gas with 1.0 mT Ar partialpressure (Ar flow at 15 sccm) and 0.30 mT N₂ partial pressure (N₂ flowat 5.55 sccm). Oxygen was leaked in with a Gransville-Phillips precisionleak valve to maintain a constant O₂ partial pressure ranging from 0.10to 0.20 mT. The thin film was deposited by RF magnetron sputtering froma five inch diameter target with a power of 450 W. Under the aboveconditions, the deposition rate was typically 0.75 to 1.6 Å/sec.

Prior to sputtering, the target was presputtered in 5 mT Ar for 5 min at450 W. Then 5 min of presputtering was performed under the depositioncondition of the thin film to precondition the surface of the target.After presputtering, the substrates were immediately loaded through aload lock chamber into the deposition chamber and deposition was carriedout. The film thickness ranged between 400 to 2000 Å depending on thedeposition conditions.

By adjusting the oxygen to nitrogen, transmission as high as 20% can beachieved at 193 nm for film thickness corresponding to 180 degree phaseshift. Such wide transmission window provides the possibility ofextending the operation wavelength down to 157 nm. FIG. 9 summarizes thefilm deposition conditions, optical properties (% T at 180 degree phaseshift, n, and k), and the resulting composition obtained from RBSanalysis.

B. Si_(w)Ti_(x)N_(y) Where as w=0.1˜0.6, x=0.01˜0.2, y=0.3˜0.6 andSi_(w)Ti_(x)N_(y)O_(z) where as w=0.1˜0.6, x=0.01˜0.2, y=0˜0.6, andz=0˜0.7 Photomask Blanks Prepared by Multitarget.

Thin films composed of Si_(w)Ti_(x)N_(y) and Si_(w)Ti_(x)N_(y)O_(z) byusing Si₃N₄ and Ti targets were deposited, with the substrate in arotating holder with planetary motion. Sputtering was carried out in anargon/nitrogen gas mixture at 1-2 mT deposition pressure with Ar flow at15 sccm and N₂ flow at 6 sccm. The Si₃N₄ target was sputtered with an RFmagnetron at a fixed power of 900 W and the Ti target was sputtered witha dc magnetron using power ranging from 0 to 200 W. Both targets were 5inch in diameter. Under the above conditions, the deposition rate wastypically 1.7 to 2.1 Å/sec.

Prior to sputtering, both targets were simultaneously presputtered in 5mT Ar for 5 min at 900 W and 400 W for the RF and DC cathodesrespectively. Then 5 min of presputtering was performed under thedeposition conditions of the thin film to precondition the surface ofthe targets. After the presputtering, immediately the substrates wereloaded through a load lock chamber into the deposition chamber anddeposition was carried out. The film thickness ranged from 400 to 2000 Ådepending on the deposition parameters.

FIG. 10 summarizes the film deposition conditions and the resultingcomposition obtained from RBS analysis. FIG. 11A summarizes the % Tcalculated for films at 180° phase shift versus the Ti target power. The% T decreases as the Ti target power increases. The increase of Ti powerincorporates more Ti into the film (see FIG. 10) which reduces the % T.The % T is tunable by varying the Ti concentration. FIG. 11B and FIG.11C summarize the n and k values as a function of Ti target powerrespectively.

While this invention has been described in terms of certain embodimentthereof, it is not intended that it be limited to the above description,but rather only to the extent set forth in the following claims. Theembodiments of the invention in which an exclusive property or privilegeis claimed are defined in the appended claims. The teaching of allreferences cited herein, are incorporated herein by reference.

What is claimed is:
 1. A method of fabricating an attenuating phaseshift mask blank for use in lithography comprising: providing asubstrate; disposing a thin layer of phase shifting layer on saidsubstrate; forming a surface layer rich in oxygen on said phase shiftinglayer; wherein said blank is capable of producing a photomask with 180°phase shift and an optical transmission of at least 0.001% at a selectedwavelenth of <500 nm; and said surface layer rich in oxygen is obtainedby oxygen plasma bombardment.
 2. A method of fabricating an attenuatingphase shift mask blank for use in lithography comprising: providing asubstrate; disposing a thin layer of phase shifting layer on saidsubstrate; forming a surface layer rich in oxygen on said phase shiftinglayer; wherein said blank is capable of producing a photomask with 180°phase shift and an optical transmission of at least 0.001% at a selectedwavelength of <500 nm; and an oxygen partial pressure of the process gasduring deposition is increased at the final stage of deposition.
 3. Amethod according to anyone of claim 1 or 2 wherein the phase shiftinglayer comprises a composite material of formula A_(w)B_(x)N_(y)O_(z),where A is an element selected from the group consisting of Groups IVA,VA, or VIA; and B is selected from the group consisting of an elementfrom Groups II, IV, V, the transition metals, the lanthanides and theactinides; wherein w is in a range between 0.1 and 0.6, x is in a rangebetween 0.01 and 0.2, y is in a range between 0 and 0.6, and z is in arange between 0 and 0.7.
 4. A method according to anyone of claim 1 or 2wherein the phase shifting layer comprises a material selected from thegroup consisting of a silicon/titanium/nitrogen composite and asilicon/titanium/nitrogen/oxygen composite.
 5. A method according toclaim 4 wherein said silicon/titanium/nitrogen composite has structuralformula Si_(w)Ti_(x)N_(y) wherein w=0.1˜0.6, x=0.01˜0.2, y=0.3˜0.6,z=0˜0.7.
 6. A method according to claim 4 wherein saidsilicon/titanium/nitrogen/oxygen composite has structural formulaSi_(w)Ti_(x)N_(y)O_(z) wherein w=0.1˜0.6, x=0.01˜0.2, y=0˜0.6, andz=0˜0.7.
 7. A method according to anyone of claim 1 or 2 wherein thephase shifting layer is formed by sputter deposition from a target of acomposite material (Si_(1-x)Ti_(x)) wherein x=0.01˜0.5 by a methodselected from the group consisting of RF matching network, DC magnetron,AC magnetron, pulsed bipolar DC magnetron and RF diode.
 8. A methodaccording to claim 7 wherein the substrate is disposed in a holder whichcan be either planetary or stationary and/or rotating or non-rotating.9. A method according to claim 3 wherein the phase shifting layer isformed by sputter deposition from a target of a composite material(Si_(1−x)Ti_(x)) wherein x=0.01˜0.5 by a method selected from the groupconsisting of RF matching network, DC magnetron, AC magnetron, pulsedbipolar DC magnetron and RF diode.
 10. A method according to claim 9wherein the substrate is disposed in a holder which can be eitherplanetary or stationary and/or rotating or non-rotating.
 11. A methodaccording to claim 4 wherein the phase shifting layer is formed bysputter deposition from a target of a composite material(Si_(1−x)Ti_(x)) wherein x=0.01˜0.5 by a method selected from the groupconsisting of RF matching network, DC magnetron, AC magnetron, pulsedbipolar DC magnetron and RF diode.
 12. A method according to claim 11wherein the substrate is disposed in a holder which can be eitherplanetary or stationary and/or rotating or non-rotating.
 13. A methodaccording to anyone of claim 1 or 2 wherein the phase shifting layer isformed by sputter deposition from two or more targets of differentcompositions using a technique selected from the group consisting of RFmatching network, DC magnetron, AC magnetron, pulsed bipolar DCmagnetron and RF diode.
 14. A method according to claim 13 wherein saidtwo or more targets are selected from the group consisting of Si₃N₄ andTi targets, or (Si_(1−x)Ti_(x)) wherein x=0.01˜0.5 and Ti targets.
 15. Amethod according to claim 13 wherein the substrate is disposed in aholder which can be either planetary or stationary and/or rotating ornon-rotating.
 16. A method according to claim 3 wherein the phaseshifting film is formed by sputter deposition from two or more targetsof different compositions using a technique selected from the groupconsisting of RF matching network, DC magnetron, AC magnetron, pulsedbipolar DC magnetron and RF diode.
 17. A method according to claim 16wherein said two or more targets are selected from the group consistingof Si₃N₄ and Ti targets, or (Si_(1−x)Ti_(x)) wherein x=0.01˜0.5 and Titargets.
 18. A method according to claim 16 wherein the substrate isdisposed in a holder which can be either planetary or stationary and/orrotating or non-rotating.
 19. A method according to claim 4 wherein thephase shifting layer is formed by sputter deposition from two or moretargets of different compositions using a technique selected from thegroup consisting of RF matching network, DC magnetron, AC magnetron,pulsed bipolar DC magnetron or RF diode.
 20. A method according to claim19 wherein said two or more targets are selected from the groupconsisting of Si₃N₄ and Ti targets, or (Si_(1−x)Ti_(x)) whereinx=0.01˜0.5 and Ti targets.
 21. A method according to claim 19 whereinthe substrate is disposed in a holder which can be either planetary orstationary and/or rotating or non-rotating.
 22. A method according toanyone of claim 1 or 2 wherein structural changes occur in said phaseshifting layer to stabilize against radiation and chemical treatment byincluding an increased surface oxygen concentration to form said surfacelayer rich in oxygen which is obtained by annealing at elevatedtemperature in an atmosphere selected from the group consisting of air,oxygen, vacuum and a mixture of gases selected from the group consistingof O₂, N₂, H₂, Ar, Kr, Ne, He, O₃ and H₂O.
 23. A method according toclaim 3 wherein structural changes occur in said phase shifting layer tostabilize against radiation and chemical treatment by including anincreased surface oxygen concentration to form said surface layer richin oxygen which is obtained by annealing at elevated temperature in anatmosphere selected from the group consisting of air, oxygen, vacuum anda mixture of gases selected from the group consisting of O₂, N₂, H₂, Ar,Kr, Ne, He, O₃ and H₂O.
 24. A method according to claim 4 whereinstructural changes occur in said phase shifting layer to stabilizeagainst radiation and chemical treatment by including an increasedsurface oxygen concentration to form said surface layer rich in oxygenwhich is obtained by annealing at elevated temperature in an atmosphereselected from the group consisting of air, oxygen, vacuum and a mixtureof gases selected from the group consisting of O₂, N₂, H₂, Ar, Kr, Ne,He, O₃ and H₂O.
 25. A method according to anyone of claim 1 or 2 whereinthe annealing can be done by using methods selected from the groupconsisting of laser annealing, plasma annealing, thermal annealing,microwave annealing and radiation treatment.
 26. A method according toclaim 3 wherein the annealing can be done by using methods selected fromthe group consisting of laser annealing, plasma annealing, thermalannealing, microwave annealing and radiation treatment.
 27. A methodaccording to claim 4 wherein the annealing can be done by using methodsselected from the group consisting of laser annealing, plasma annealing,thermal annealing, microwave annealing and radiation treatment.
 28. Amethod according to claim 2 wherein the surface layer rich in oxygen isobtained by oxygen plasma bombardment.
 29. A method according to claim 3wherein the surface layer rich in oxygen is obtained by oxygen plasmabombardment.
 30. A method according to claim 4 wherein the surface layerrich in oxygen is obtained by oxygen plasma bombardment.
 31. A methodaccording to claim 3 wherein an oxygen partial pressure of the processgas during deposition is increased at the final stage of deposition. 32.A method according to claim 4 wherein an oxygen partial pressure of theprocess gas during deposition is increased at the final stage ofdeposition.
 33. A method according to anyone of claim 1 or 2 wherein thesputter target is made by hot isostatic pressing.
 34. A method accordingto claim 3 wherein the sputter target is made by hot isostatic pressing.35. A method according to claim 4 wherein the sputter target is made byhot isostatic pressing.
 36. A method according to anyone of claim 1 or 2wherein the sputter target is made of a mixture of metal silicide andsilicon.
 37. A method according to claim 3 wherein the sputter target ismade of a mixture of metal silicide and silicon.
 38. A method accordingto claim 4 wherein the sputter target is made of a mixture of metalsilicide and silicon.
 39. A method according to anyone of claim 1 or 2wherein the sputter target is made of a mixture of titanium silicide andsilicon.
 40. A method according to 3 wherein the sputter target is madeof a mixture of titanium silicide and silicon.
 41. A method according toclaim 4 wherein the sputter target is made of a mixture of titaniumsilicide and silicon.